Method of making composite metal bodies.



I W D; COOLIDGE. I METHOD OF MAKING "OMFOSITE METAL BODIES.

' APPUCATION FILED AUG.2I. 1912.

1,162,313 9 rammed Nov. 30, 1915.

"Fig.l.

WZTNE55E5 .1 [7V YENTL'YH IWJ LLIAMZZ 501121753,

H fi $2; @SZTTDHNEY To all whom it may concern:

' UNITED ST TES arana 1 OFFICE.

WILLIAM D. COOLIDGE, OF SCHENECTADY, NEW YORK, TO GENERAL ELECTRIC,COMPANY, A CORPORATION OF NEW YORK.-

Application filed August 21,

Be it known that'I, WILLIAM-D. CooLIncE, a citizen of the Uni-tedStates, residing at Schenectady, county of Schenectady, State of NewYork, have invented certain new and useful Improvements in Methods ofMaking Composite Metal Bodies, of which the following is aspecification.

My present invention. relates to a process of joining metals. Though the-method or process isof general application I find it particularlyuseful in making joints between copper or other low melting pointnietaland a body of material-such as wrought tui gsten, the qualities of whichare apt to be 1njured if the body is submitted to an excessively hightemperature.

OneLparticuIaruse to which my invention may be put is in the manufactureof X-ray- I targets'in which a massive body of copper is commonlyemployed to which in some suitable way the target proper,.usually ofrefractory .metal, is fastened. This has h'eretoforebeendone by ordinarysoldering methods, but these methods are objectionablefi; I invention inone of its aspects consists of an X-ray target in which the active face1 is formed of wrought tungsten adhering to amass of copper withoutintervening sol-- dering ,material. In other words, the wrought tungstenis autogenously joined to the copper and this I accomplis way that thetungsten itself heated to such a temperature "fiwould impair thecharacteristics of the wrought metal. Where my invention is applied tothe manufacture of such an X-ray target, I may proceed as follows,reference-being had to the accompanying drawings in which- Figure 1illustrates an apparatus for carrying out my invention and Fig. 2 anX-ray target representing one form of embodiment of my invention.

I have found that it is possible under suitable conditions to castcopper into contact with a body of wrought tungsten so that, uponcooling, the copper will be found to have wet the surface of thetungstenand to be strongly adherent thereto. This has here tofore'been done byme as set forth in my f prior application, Serial No. 685,113, filed 7March 20, 1912, by placing the copper and i I Specification of LettersPatent.

wrought tungsten,

closed at the bottom METHOD OF MAKING- COMIQOSITE METAL'BODIEG.

1912. serial Nb. 716,206.

' ing the parts in a vacuum furnace not only to the melting point ofcopper but to a very much higher temperature in order to drive out allof the gas in the copper so as to avoid oxidation of the surface of thetungsten which would otherwise. interfere with the joiningof the parts.Instead of heating the copper in a vacuum furnace as described thedegasifying of the copper can be done by a. boronizing process as setforth in U. S. Patcut to E. VVeintraub, No. 1,023,604, April 16, 1912,consisting for example in the addition to the copper either of boron orof boron oxid of a state of oxidation lower than the anhydrid, andheating the parts to a high temperature. Copper thus trcTzied ishomogeneous, free from blow-holes and sound in structure. While' both ofthese methods serve effectively to produce good joints between thetungsten and the body of copper, they both have the disadvantage thatthe temperature necessary for the de-,

to imp-air the quali gasifying is so high as ties of the wroughttungsten. To avoid this disadvantage, I degasify the copper or othermetal separately, as by the use of the boronizing casting process abovementioned. The degasified copper is then cast into sticks or pieces ofconvenient size. These sticks or pieces are then placed in a mold alongwith the tungsten body into contact with which it is desired .to castthe copper, and the mold and its contacts are placed in a Vacuum-furnaceto avoid the action of oxygen and heated to the melting point of copper.The copper, already-degasified, flows against and about the tungstenbody, wets the surface thereof, and upon cooling will be found tohaveformed a perfect joint therewith. The

not hai ingbeen excessiv'ely heated. by this 'method of procedure,retains its properties unimpaired or substantially so.

In Fig.1 of the drawings, I haveshown a mold intended-especially forproducing X-ray targets by. this method The container or mold 'for themetal to be melted consists of a cylindrical vessel 1 and madepreferably of artificial graphite though other suitable material may beemployed if desired. In the bottom of this mold or container, is placeda block of graphite 2 of cylindrical shape but having its top surfacecut ofl at an angle, as indicated. This leaves the upper Patented Nov-30, 1915.

heldin place during the casting operation by a small pin 4, which passesthrough the i wall of the mold '1 and enters a hole drilled in the block2 This is for the purpose of preventingthe block 2 from being floatedout of the mold by the molten metal.

The small disk of Wrought tungsten which is-to form the active surfaceof :the X-ray target is held in place, duringthe casting operation, onthe center of the surface 3 of the block 2., i This tungsten targetproper is indicated at 5, and a convenient means for holding it in placemay consist of two small pins -6 and 7 of tungsten wire held incorresponding holes drilled into the block 2 so that the disk 5 will besupported between them. The parts. as thus described constitute thearrangement of the mold before the a metal is inserted. The copper metalof which the body of the target is to be formed is previously preparedpreferably in a piece which may be loosely inserted in the mold. Themetal thus used is metal which has been previously degasifiedpreferablyby the use of the boron treating process referred toabove. Apiece of such metal in place ready for themeltingoperation is indicatedat 8.

The parts being thus assembled, the mold and its contents areheated in avacuum furnace of any suitable form such as that disclosed in patent ofArsem, No. 785,535. Obviously, as many such molds may be heated at onetime as may be desired and as the capacity of the furnace may permit, sothat the process may be practised on a large scale. After the molds areplaced in the vacuum furnace the temperature is raised until the copperis well melted but it is not raised any higher than'necessary for thispurpose so as to avoid injuring the wrought tungsten by depriving itmore or less of the characteristics of density, strength, fibrousnessand toughness due to its mechanical working. The copper having beenmelted as described fills the mold closely, wets the surfaces of thetungsten and runs into close contact' therewith. Upon cooling andremoval of the mold from the furnace the parts are readily disassembledand the cast member is then machined into suitable form such asindicated in Fig. 2. In this form the X-ray is turneddown to acylindrical shape at 9 and with a shank 10 for attachment to thesupporting means for thetarget. The tungsten surface of the target isindicated at 5 as before and the pins which support it during thecasting operation are indicated,

as before, at 6 and 7. These pins remain in the target and are machined.off during the operation of smoothing up the face of the target.

While I have described my invention with particular reference to itsapplication to the manufacture of targets of X ray tubes, and while oneof the embodiments of my invention consists of atarget so made andhaving the novel properties not heretofore obtained, my invention isnevertheless applicable for many other purposes where a body of metalsuch as copper is to be provided with a working surface say of wroughttungsten,

as in the manufacture of electrical contacts and the like, and Itherefore do not wish to be limited to the exact details as set forthherein.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is z- 1. The method of producing a composite metal body, one ofthe. metals being a wrought metal and the other having a melt- 'ingpoint of relatively low value, which consists in degasifying' the lowmelting point metal and after it has been degasified bringing it whilein a molten condition into contact with the wrought metal, at atemperature not materially higher than the melting point of thedegasified metal.

2. The method of producing a composite metal body, I one of the metalsbeing a wrought metal, and .the other having a melting point ofrelatively low value, which consists in degasifying the low meltingpoint metal and after it has been degasified bringing it while in amolten condition into con.

tact with the wrought metal in a vacuum, at a temperature not materiallyhigher than necessary to secure fluidity of the degasified metal.

3. The method of producing a composite metal body, one of the metalsbeing Wrought tungsten, and the other having a melting point ofrelatively low value, which consists in, degasifying the low meltingpoint metal and after it has been degasified bringing it while in amolten condition into contact with the wrought tungsten, the temperatureof the molten metal being not substantially greater than that necessaryto secure fluidity of the metal.

4." The method of'casting copper into contact with wrought tungstenwhich consists in first degasifying the copper, and then bringing thecopper thus degasified, at a temperature not materially above themelting point of copper, into union with the wrought tungsten, whereby acomposite metal body is produced.

' 5. The method of producing a composite metal body, one of the metalsbeing a wrought metal, and the other a relatively u 125 low meltingpoint metal which consists in bringing the low melting point metal into,

union with the wrought metal at a tempera ture not materially higherthan that of the melting point of the lower melting point metal, the lowmelting point metal having been previously degasified' whereby theWrought metal is not at any time during the process brought to atemperature higher than that corresponding to about the melting point ofthe low melting point metal.

6. The method of producing a composite metal body, one of the metalsbeing of Wrought tungsten, and the other of copper which consists inbringing the copper into union With the Wrought tungsten at atemperature not materially higher than that of the melting point of thecopper, the copper having been previously degasified, whereby thewrought tungsten is not at any time during the process-brought to atemperature higher than that corresponding to about the melting point ofthe copper.

7. The method of uniting Wrought tungsten With copper, While retainingthe physical properties pf the Wrought tungsten, which consists in firsttreating the copper with oXidiZable boron material to degasify thecopper and then bringing the copper in a molten condition into contactwith the tungsten in a vacuum at a temperature not substantially higherthan that necessary to secure fluidity of the copper.

In Witness whereof, I have hereunto set my hand this 20th day of August,1912.

WILLIAMVD. COOLIDGEQ r Witnesses: BENJAMIN B. HULL, MARGARET E. WOOLLEY.

